Magnesium battery : Current trends and future perspectives
ABSTRACT:-
Lithium-ion batteries have enabled electric vehicles to achieve a foothold in the automobile market. Due to an increasing environmental consciousness, electric vehicles are expected to take a larger portion of the market, with the ultimate goal of supplanting traditional vehicles. However, the involved costs, sustainability, and technical limitations of lithium-ion batteries do create substantial obstacles to this goal. Therefore, this article aims at presenting magnesium-ion batteries as a potential replacement for lithium-ion batteries. Though still under development, magnesium-ion batteries show promise in achieving similar volumetric and specific capacities to lithium-ion batteries. Additionally, magnesium is substantially more abundant than lithium, allowing for the batteries to be cheaper and more sustainable. Numerous technical challenges related to cathode and electrolyte selection are yet to be solved for magnesium-ion batteries. This paper discusses the current state-of-the-art of magnesium-ion batteries with a particular emphasis on the material selection. Although current research indicates that sulfur-based cathodes coupled with a (HMDS)2Mg-based electrolyte shows substantial promise, other options could allow for a better performing battery. This paper addresses the challenges (materials and costs) and benefits associated with developing these batteries. When overcoming these challenges, magnesium-ion batteries are posed to be a groundbreaking technology potentially revolutionizing the vehicle industry.
INTRODUCTION:-
Magnesium batteries are batteries that utilize magnesium cations as the active charge transporting agent in solution and as the elemental anode of an electrochemical cell. Both non-rechargeable primary cell and rechargeable secondary cell chemistries have been investigated. Magnesium primary cell batteries have been commercialised and have found use as reserve and general use batteries.
Magnesium secondary cell batteries are an active topic of research, specifically as a possible replacement or improvement over lithium-ion–based battery chemistries in certain applications. A significant advantage of magnesium cells is their use of a solid magnesium anode, allowing a higher energy density cell design than that made with lithium, which in many instances requires an intercalated lithium anode. Insertion type anodes ('magnesium ion') have also been researched.
The main innovation supporting this effort is the electric vehicle (EV), which has been a work-in-progress since the 1830s. Over the past two centuries, several factors have contributed to the fluctuating popularity of electric cars, but it was not until the 1990s that new environmental regulations sparked modern interest in this alternative. Since then, models such as the 1996 GM EV1, the 2000 Toyota Prius, the 2008 Tesla Roadster, and the 2010 Nissan Leaf have prompted widespread application and increased recognition. Today’s most popular EV is the 2020 Tesla Model 3, which is the first vehicle to outsell its gasoline-run counterparts. The transition from gasoline to electric vehicles has been proven to downsize the amount of pollution being emitted into the atmosphere. Indeed, the average EV produces approximately only a third of the global warming pollution of similar gasoline-powered vehicle. The widespread success of the EV is based on the underlying battery chemistry. As the EV market was growing, it had to leverage available rechargeable battery technologies. For instance, the Tesla Model S used 7100 Panasonic 18,650 batteries, which is the common battery used in devices ranging from laptops to e-cigarettes. The recent success of EV is tied to the high energy densities and power capacities achieved from lithium-ion batteries. As EVs usage is likely to take over a large portion of the automobile market, it can now lead the battery development efforts. One battery chemistry in particular, magnesium-ion, would offer future EVs numerous advantages over lithium-ion.
Scientists have investigated numerous metals to replace lithium in batteries. These elements include sodium, potassium, aluminum, zinc, and calcium. Though several of these metals showed promise, magnesium came out as having many of the properties that would make for an attractive replacement for lithium.
One of the most promising characteristics of magnesium is that it is divalent, such that the oxidation step would result in two electrons and a Mg2+ ion. The divalent nature of magnesium results in a high specific capacity and volumetric energy density. In particular, the theoretical volumetric capacity of a magnesium-ion battery is 3833 mAh/mL, which nearly doubles the volumetric capacity of lithium (2062 mAh/mL), as shown in Figure . Note that these values are the theoretical maximum values and in practicality, lithium-ion batteries have a volumetric capacity less than 200 m Ah/mL. However, the higher theoretical volumetric capacity indicates an increased likelihood for a higher practical value.
Since magnesium is heavier than lithium, the battery will naturally be heavier for a given energy capacity. Indeed, the theoretical energy density of a magnesium-ion battery is 2205 mAh/g compared to 3861 mAh/g for lithium-ion. However, in practicality, lithium-ion batteries are achieving less than 150 mAh/g. Early tests have shown that with a sulfur cathode, a magnesium-ion battery can achieve 1000 mAh/g. Given that most EVs are space and weight constrained, the use of magnesium-ion batteries could potentially increase the range of the vehicle.
In addition to the increased energy capacities, magnesium-ion batteries have numerous other advantages over lithium-ion. First, magnesium does not tend to form dendrites, resolving the safety issues associated with lithium-ion batteries. As such, a magnesium-ion battery can last substantially longer than a lithium-ion battery. Additionally, magnesium-ion batteries can be charged faster since lithium-ion batteries charge times are constrained to avoid dendrite formation. Magnesium is also reported to be the eighth most abundant element on earth’s crust,21 eliminating the depletion risk, and granting a much cheaper product. Moreover, magnesium is safer than lithium. Since magnesium does not form toxic compounds, manufacturing magnesium-ion batteries would be more cost-effective and environmentally friendly than lithium-ion batteries. Thus, the transition from lithium to magnesium will provide the opportunity to store energy more efficiently at a lower cost.
Magnesium as a Resource:-
The future of magnesium-ion batteries:-
Conclusion:-
Mg batteries are one of the few options to complement or even replace Li ion batteries in the future. Although the basic properties of the Mg anode are promising, such as the bivalency of the Mg ion, the high volumetric storage capacity of the anode, the non-toxicity of Mg, and the lack of dendrite formation which allows the building of batteries with a metal anode, battery cells with competitive properties have not yet been reported. This is mostly due to the lack of suitable cathodes allowing high capacities and voltages and the presence of overpotentials, especially during plating and capacity fading due to unstable electrolytes and/or unstable electrodes. The research to address all of these issues in order to realize viable solutions is exciting and so far, no dead-ends are in sight, so the success of this technology will largely depend on the skills and effort that are put into this fascinating field of energy research and technology.
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